Fine solid needles (acupuncture needles) are inserted into taut, tender muscle bands, or or specific injured sites that have become irritated and supersensitive. Penetration of a normal muscle is painless; however, a shortened, damaged muscle will ‘grasp’ the needle in what can be described as a cramping sensation. The needling will stimulate stretch receptors in the muscle producing a relaxation or lengthening reflex. The needling also causes small injury to the area, initiating the natural healing process.